fsharp/step4_if_fn_do.fs

   1 module REPL
   2     open System
   3
   4     let read input =
   5         try
   6             Reader.read_str input
   7         with
   8         | Types.ReaderError(msg) ->
   9             printfn "%s" msg
  10             []
  11
  12     let eval env ast =
  13         try
  14             Some(Eval.eval env ast)
  15         with
  16         | Types.EvalError(msg) ->
  17             printfn "%s" msg
  18             None
  19
  20     let print v =
  21         v
  22         |> Seq.singleton
  23         |> Printer.pr_str
  24         |> printfn "%s"
  25
  26     let rep env input =
  27         read input
  28         |> Seq.ofList
  29         |> Seq.choose (fun form -> eval env form)
  30         |> Seq.iter (fun value -> print value)
  31
  32     let getReadlineMode (args : string array) =
  33         if args.Length > 0 && args.[0] = "--raw" then
  34             Readline.Mode.Raw
  35         else
  36             Readline.Mode.Terminal
  37
  38     [<EntryPoint>]
  39     let main args =
  40         let mode = getReadlineMode args
  41         let env = Env.makeRootEnv ()
  42         let rec loop () =
  43             match Readline.read "user> " mode with
  44             | null -> 0
  45             | input ->
  46                 rep env input
  47                 loop ()
  48         loop ()